Discourse Structure Grosz and Sidner

Why bother? Leads to an account of discourse meaning Constrains how utterances are related Useful for explaining interruptions and the purpose of discourse participants

Linguistic Structure of the sequence of the utterances Discourse segments Utterances within a segment contribute to a common purpose Drawback: hard to figure out segmentation Clues: pause lengths, cue words, use of referring expressions

Intentional Discourse Purpose – reason why discourse happens in the first place Discourse Segment Purpose – how a segment contributes to the DP Relations –Dominance (DSP1 dominates DSP2) –Satisfaction Precedence (DSP1 sat-pre’s DSP2)

Attentional Different: property fo Discourse not participants “abstraction of the participants’ focus of attention as their discourse unfolds” Dynamic stack that records salient objects, properties and relations Focusing – process of manipulating focus spaces on attentional (focus) stack

Attentional DS’s tied to focus spaces. Pushed and popped off stack depending on dominance hierarchy Focus stack: only what is relevant at that time, Intentional – complete record At end of discourse, focus stack is empty Only attentional state constrains referring expressions

Processing Issues How does OCP judge segmentation? Intention recognition: –Cue phrases –Utterance level intentions –Shared knowledge about actions and objects in domain

Processing Issues Recognition complete at end of segment But OCP must be able to recognize a generalization of DSP Focus Stack: –Constrain range of DSP’s for relating to current DSP –Constrain search for possible referents (centering)

Interruptions True Interruptions Weak Interruptions/Flashbacks Digressions